unit 17: review all the things. part i. lpchem1415 groups of similar elements have special names:

Unit 17: ReviewAll the Things.

Part I

LPChem1415

Groups of similar elements have special names:

LPChem1415

# valence electrons increases, left to right:1 2 3 4 5 6 7 8

LPChem1415

Valence Electrons & Stability

Main Group Ion Charges1+

2+ 3+4± 3- 2- 1-0

Positive charge means electrons were REMOVED. Negative charge

means electrons were ADDED.

LPChem1415

Ionic Nomenclature: Roman NumeralsFe2 (CO3)3 = iron ( ? ) carbonate

Fe2 (CO3)3 2-

6-

( ) 3

= 06+

( )2 +3+

Iron (III) carbonate

C. Molar Conversionsmolar mass

(formula mass)

(g/mol)

MASSIN

GRAMS

MOLESNUMBER

OFPARTICLES

Avogadro6.02 1023

(particles/mol)

C. Molar Conversionsmolar mass

(formula mass)

mass (grams) FM

MASSIN

GRAMS

MOLESNUMBER

OFPARTICLES

Avogadro6.02 1023

Particles Avogadro= moles =

A. Molarity 1. Concentration of a solution.

solution of literssolute of moles(M)Molarity

total combined volume

substance being dissolved

B. Molality 1. Concentration of a solution.

solvent ofkg solute of moles(m)Molality

Mass of solvent

substance being dissolved

What is the percent composition of Cu2S?

Copper: 2(63.55) / 159.16 =

Cu2S has a molar mass of:

A. Percentage Composition

2(63.55) + 32.06 = 159.16

0.7986 = 79.86 % Cu

Sulfur: 1(32.06) / 159.16 = 0.2014 = 20.14 % S

C. Johannesson

B. Empirical Formula

C2H6

CH3

reduce subscripts

Smallest whole number ratio of atoms in a compound

C. Johannesson

B. Empirical Formula1. Find mass (or %) of each element.

2. Find moles of each element.

3. Divide moles by the smallest # to find subscripts.

4. When necessary, multiply subscripts by 2, 3, or 4 to get whole #’s.

C. Johannesson

B. Empirical Formula Find the empirical formula for a

sample of 25.9% N and 74.1% O.

25.9 g 1 mol14.01 g

= 1.85 mol N

74.1 g 1 mol16.00 g

= 4.63 mol O

1.85 mol

1.85 mol

= 1 N

= 2.5 O

C. Johannesson

B. Empirical Formula

N1O2.5Need to make the subscripts whole

numbers multiply by 2

N2O5

C. Johannesson

C. Molecular Formula “True Formula” - the actual number

of atoms in a compound

CH3

C2H6

empiricalformula

molecularformula

?

C. Johannesson

C. Molecular Formula1. Find the empirical formula.2. Find the empirical formula mass.3. Divide the molecular mass by the

empirical mass.4. Multiply each subscript by the

answer from step 3.

nmass EFmass MF

nEF

C. Molecular Formula The empirical formula for ethylene

is CH2. Find the molecular formula if the molecular mass is 28.1 g/mol?

28.1 g/mol14.03 g/mol

= 2.00

empirical mass = 14.03 g/mol

(CH2)2 C2H4

C. Johannesson

A.Signs of a Chemical Reaction Evolution of heat and light Formation of a gas Formation of a precipitate Color change

C. Johannesson

B.Law of Conservation of Mass mass is neither created nor destroyed

in a chemical reaction

4 H

2 O

4 H

2 O4 g 32 g

36 g

total mass stays the same atoms can only rearrange

C. Johannesson

C. Chemical Equations

A+B C+DREACTANTS PRODUCTS

C. Johannesson

Al + CuCl2 Cu + AlCl3

Al

Cu

Cl

1 1

1 1

2 3

2

3

6

3

33 2

C. Balancing ExampleAluminum and copper(II) chloride react to form copper and aluminum chloride.

2

2

6

D. Stoichiometry Problems How many moles of KClO3 must

decompose in order to produce 9 moles of oxygen gas?

9 mol O2 2 mol KClO3

3 mol O2

= 6 mol KClO3

2KClO3 2KCl + 3O2 ? mol 9 mol

D. Stoichiometry Problems How many grams of silver will be

formed from 12.0 g copper?

12.0g Cu

1 molCu

63.55g Cu

= 40.7 g Ag

Cu + 2AgNO3 2Ag + Cu(NO3)2

2 molAg

1 molCu

107.87g Ag

1 molAg

12.0 g ? g